Diastereoselective Vinyl Addition to Chiral Hydrazones via Tandem Thiyl Radical Addition and Silicon-Tethered Cyclization
作者:Gregory K. Friestad、Sara E. Massari
DOI:10.1021/ol0067991
日期:2000.12.1
A diastereoselective method for addition of a vinyl group to alpha-hydroxy hydrazones under neutral tin-freeradicalcyclizationconditions, leading to substituted vinylglycinols, is presented. Tandem thiyl radical addition/cyclization upon a silicon-tethered vinyl group followed by treatment with potassium fluoride accomplishes a one-pot neutral vinyl addition process to afford acyclic allylic anti-hydrazino
Tandem thiyl radical addition and cyclization of chiral hydrazones using a silicon-tethered alkyne
作者:Gregory K. Friestad、Tao Jiang、Gina M. Fioroni
DOI:10.1016/s0957-4166(03)00540-8
日期:2003.10
A diastereoselective method for addition of a trans-2-(phenylthio)vinyl group to α-hydroxy hydrazones is presented. An ethynyl group, tethered to α-hydroxy hydrazones via a silicon tether, undergoes thiylradicaladdition and cyclization under neutral tin-free conditions. In the same pot, desilylation with potassium fluoride or tetrabutylammonium fluoride affords (E)-vinylsulfides. The one-pot process
A Silicon Tether Approach for Diastereocontrol in Radical Addition to Chiral Hydrazones
作者:Gregory K. Friestad
DOI:10.1021/ol991059h
日期:1999.11.1
A radical carbon-carbon bond construction approach to chiral a branched amines is presented. Stereocontrolled radical addition to chiral hydrazones can be achieved by virtue of conformational constraints imposed during cyclizations using a temporary silicon connection. Oxidative removal of the tether completes the hydroxymethylation process to afford anti-2-hydrazino-1,3-diols in good yield. The 1,2-induction increases with increasing A values of the appended groups, consistent with prediction by the Beckwith-Houk model for stereocontrol in 5-hexenyl radical cyclizations.